There's not great way to do this, so I'll just handle it in little zones.
Let's start with the abandoned area, even though you won't go to it for a bit. When you walk back through the caged walkway, a trog will knock a section of it off and be lying in wait. Kill it and walk into the side area. 3 ingots are lying in a cart. 3
Start by grabbing the first 2 ingots next to the dead slave at the start. You probably already did this. Go forward and go around the supply plant. Keep following the tracks to the back corner with the group of trogs. Kill them and grab the 2 ingots here. Look over to the dumpsters. 4
Go forward and climb onto the truck. Jump into the first dumpster to get 2 ingots. Get onto the raised part and jump into the next dumpster for another 2 ingots. Look for another 3 ingots in another smaller dumpster by the next one in the line. 7
Go up the first step of steps for some more ingots in the raised section. We'll go to the right first. Climb the steps and go over the fallen fence. Go to the right and turn down the alley. 2 steel ingots are lying by a pile of barrels. Go out of the alley and move along the fence. Carefully walk out onto one of the steel beams and drop down onto the train cars. There are 2 ingots lying on top of one of the train cars. Move along the boards and look for a dumpster below one of them. Drop in to grab another 3 ingots. Move back up and go to the left now. Enter the small steel shack and grab the 2 ingots off of the shelf. Walk out and go through the gate. 9
This next area has a lot of ingots in spread out locations. First, look for the one large dumpster near all of the fences. Climb the nearby stairs and jump into it for 2 ingots. Jump out and over the fence sealing off the sections of generators. There are 2 ingots waiting here. Climb onto the board resting on the generator to leave the fenced in area. 4
Go back and look for a square building with stairs in the back left area of the steelyard. Go up the stairs or go into the side alley. It doesn't matter. Kill the three trogs in the center and grab the 2 ingots on the ground. Go out of the alley and walk down the slight slope to get to a dead slaver lying near two ammunition boxes. Grab the 3 ingots near him, grab his armor, and get some ammo from the boxes. Look over to the left and into the radiation field. Go in along the right side and hug the wall. Kill the few trogs and then rush out to the center area. Grab the 3 ingots lying on the ground and then run back out. 8
Go back out and look for the giant bridge connecting a few of the rooftops. It should be easy to see. Climb the stairs and cross over to the bridge. There are 2 ingots lying on the center of the bridge. Finishing crossing it to what should be an unvisited building on the other side. Look around as you reach the end. There are 2 ingots lying on a nearby roof that you should be able to reach. Drop down further to land by some shelves. Another 2 ingots are lying on them. Finally, round the corner to get 2 more ingots that are hidden in a pile of tires. 8
For lack of better directions, go further to the back right and go along a small alley to the far corner. Go along this narrow path and kill the surviving trogs and Wildmen. 4 ingots are in a mine cart at the end of the alley. Hug the fence and back toward the train cars, without leaving this area. You should find 2 ingots next to a dead slave. 6
Go to the far left area near the generators and look for the one staircase. A slave named Wild Bill is here. Grab the 2 ingots by him. Make sure you also get his pistol. Continue up to the next area. 2